Application of a multidisciplinary approach to investigate on a possible secondary soil salinization due to seawater intrusion dynamics at the Volturno river mouth
Author(s)
Esposito, Raffaella
Date Issued
April 10, 2017
Type
Doctoral Thesis
Abstract
The coastal areas are characterized by high population rates and vivid economic activity. This involves a continuous increasing of water demand, often associated with a non-sustainable exploitation of the water resource.
For this reason, frequently, groundwater located near the coast are compromised by the saltwater intrusion.
In this PhD thesis, we would like to introduce a pilot study for investigating on a possible secondary salinization at the Volturno river mouth. The study comes as a result to reply to the testimonies of the local population, who reported an impairment of water quality and soil, consequently.
In our study area, we are in presence of severe pumping, which is mainly due to the urban and agricultural activity. Furthermore, thanks to previous research carried out in the same study area, a lowering of the river bed relative to sea level has been proved. These two elements suggest that salinization could be favored by up-coning phenomenon and lateral ingression through the river bed.
As a first step, site investigations were carried out, including inspections to choose the study area, interviews with local people (in order to get information not available from published sources) and photographic reports.
The second step was designing an experimental study - based on a multidisciplinary approach - in order to better address a very complex topic such as the salinization due to seawater intrusion.
Along a chosen transect, crossing three different ecosystems, with different degrees of naturalness (coastal, urban and agricultural), several measurements and samplings were carried out, and the elm tree species (Ulmus minor Mill.) was selected as bio-indicator. The multidisciplinary approach is based on:
analysis of carbon and oxygen stable isotope compositions and discrimination,
leaf gas exchange measurements on elm,
normalized difference vegetation index (NDVI) calculations;
geophysical investigations.
Such a composite approach revealed a rather complex system along the riverine transect.
Since this is a pilot study, which has clashed with practical problems due to the lack of cooperation from part of citizens and local authorities as well, the reported data are meant to be preliminary. Preliminary results did not show any salinization emergency but proved salt presence in some of the ecosystem compartments, suggesting, in addition, that saltwater presence seems to be due to both a lateral intrusion through the river’s meanders and to an improper management of water and irrigation practices. Despite all, they do not allow to discriminate which is the main phenomenon regulating the entire salinization process.
Our analyses indicate that water enriched with the heavier oxygen isotope affects photosynthesis, stomatal aperture and electron transport efficiency. In particular, the decrease of photosynthesis in the rural area suggests that the different land-uses play an important role.
Furthermore, high resolution ERTs confirmed salt water’s presence into the groundwater.
The initial phase of this pilot study confirmed the validity and potential of our approach and, at the same time, have shown the need to plan monitoring activities in the Volturno coastal area. Of course, additional measurements campaigns and experiments will be required; in that regard, we listed some proposals for a monitoring study (reported at the end of this work), which will also be presented to the competent authorities.
Another essential question is the need to inform and educate the citizens to adopt sustainable management of land and resources, remarking that the salinization hazard is a serious threat to the economy.
The study was part of research activities promoted by high technology infrastructure for environmental and climatic monitoring (PON I-AMICA).
Additional information
Dottorato di ricerca in Ecologia forestale
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